1. Field
The disclosed concept relates generally to electrical switching apparatus and, more particularly, to electrical switching apparatus such as, for example, circuit breakers. The disclosed concept also relates to pole shaft assemblies for circuit breakers.
2. Background Information
Electrical switching apparatus, such as circuit breakers, provide protection for electrical systems from electrical fault conditions such as, for example, current overloads, short circuits, abnormal voltage and other fault conditions. Typically, circuit breakers include an operating mechanism, which opens separable electrical contacts to interrupt the flow of current through the conductors of an electrical system in response to such fault conditions as detected, for example, by a trip unit.
Among other components, the operating mechanisms of some low and medium voltage circuit breakers, for example, typically include a closing assembly and an opening assembly that are structured to close (e.g., contacts electrically connected) and open (e.g., contacts separated), respectively, the separable contacts. Specifically, the operating mechanism includes a pivotable pole shaft, a number of stored energy devices such as, for example, an opening spring and a closing spring, and a latch assembly that cooperates directly or indirectly with the pole shaft to facilitate desired movement of the separable contacts.
The pole shaft generally includes an elongated shaft and a number of throws that extend outwardly from and pivot with the elongated shaft to actuate or otherwise cooperate with a variety of different circuit breaker components such as, for example and without limitation, a trip paddle of the trip assembly. The throws are typically welded to the elongated shaft. In order for the operating mechanism to operate properly, a precise trip paddle force is required. Therefore, the throws must be precisely and accurately positioned as the parts are welded together. Any shifting or warping of the components results in a change of the forces applied by the pole shaft throws.
There is room for improvement in electrical switching apparatus, such as circuit breakers, and in pole shaft assemblies therefor.